“What’s this?” Clara asked, scrutinising a complicated looking formula scrawled in Gallifreyan numbers and symbols on the Doctor’s blackboard.
“That? Oh, I was just doodling.”
“Yeah, but what is it?”
“Basic Gallifreyan mathematics; the Felloraxic Constant. It calculates the ratio of a circle’s circumference to…”
“To its diameter. Yeah, we have that too, but we call it Pi.”
“Humans have mastered the Felloraxic Constant?” the Doctor asked in disbelief.
“You didn’t know?”
“Never thought to ask.”
“A fellow named Archimedes, somewhere around 250 BC in ancient Greece. Maybe you’ve heard of him?”
“Ah, that explains it. Archimedes was an alien.”